MMA superstar Conor McGregor has signed a contract to fight unbeaten boxing champ Floyd Mayweather, but the latter has yet to follow suit. AP

WHILE fight fans await Floyd Mayweather's response to an offer to fight UFC champ Conor McGregor, Bob Arum just gave them an enticing alternative.

According to TMZ Sports, the veteran boxing promoter said his prized ward, Manny Pacquiao, is willing to fight the MMA superstar if Mayweather doesn't take a highly anticipated fight that is expected to yield half a billion dollars in revenue, if not beyond.

Arum added Pacquiao's schedule is very much open beyond his scheduled title fight against Australian underdog Jeff Horn in Brisbane on July 2, hinting a McGregor fight can be arranged.

McGregor, 28, has come to terms with UFC on a fight against Mayweather - the first step in what fans hope would be a blockbuster cross-sport showdown.

"The first, and most important part of this historic contract has now officially been signed off on. Congratulations to all parties involved. We now await [Mayweather's adviser] Al Haymon and his boxer's signature in the coming days," said McGregor.

The unbeaten Mayweather has previously hinted that a McGregor fight is the only logical option for him, but has been eerily silent since McGregor signed in the dotted line.